This invention relates to combined side pincushion and linearity correction magnetic structures and circuits.
In typical color television receivers, two separate magnetic components are connected in series with the horizontal deflection winding, namely, a linearity coil and an East-West or side pincushion correction coil or transformer. The linearity coil may be wound on a rod or H-core with one or more bias magnets located adjacent the core. The East-West coil may be wound on a separate ferrite rod core or on a closed core like a UU or an EE-core. The East-West coil may be part of an ITR controlled E-W modulator circuit such as described in U.S. Pat. No. 4,088,931 by P. E. Haferl or may be part of a diode modulator circuit such as described in U.S. Pat. No. 3,906,305 by A. H. H. J. Nillesen.
East-West correction results in a vertical rate modulation of the horizontal deflection or scanning current. The vertical rate modulation of the horizontal scanning current, however, causes an undesirable vertical rate modulation of the magnetic bias of the linearity coil. The effect of the linearity coil is thus different at the top or bottom of the raster than in the center, resulting in uncorrected raster distortion. To correct for this effect, the linearity coil biasing is sometimes modulated at a vertical rate by coupling the E-W modulator current through an extra winding on the linearity coil, as described, for example, in U.S. Pat. No. 4,024,432, by A. Boekhorst.
It is desirable, however, to combine the functions of both side pincushion correction and linearity correction into one structure which also eliminates the aforementioned raster distortion.